Daltoniaceae Schimp.

The following family description draws from Buck (1988).

Plants small to medium-sized, mostly glossy, erect or prostrate, rarely layering, pale green to gold- or red-green, forming turves or mats, rarely reduced to a persistent protonema. Stems in cross-section lacking a central strand and mostly with cells similar throughout. Leaves differentiated (dimorphic) or not, and if so the lateral ones larger, often complanate, lanceolate to broadly spathulate, plane at margins, usually bordered by elongate cells, entire or toothed; laminal cells short, smooth, mostly firm-walled; alar cells not differentiated. Costa mostly single and often percurrent (variable in N.Z. taxa), often bifurcate above or weak and bifurcate near the base. Gemmae sometimes borne in axillary clusters, at leaf margins, or on a terminal pseudopodium. Paraphyllia lacking. Pseudoparaphyllia present or lacking.

Mostly autoicous (but often dioicous in N.Z.). Setae elongate, smooth, mammillose, or spinose; capsules erect to horizontal, smooth or mammillose; exothecial cells collenchymatous; annulus present or absent; operculum conic-rostrate. Peristome double; exostome teeth narrowly bordered, on outer surface either with a median furrow and cross-striolate or lacking a median furrow and papillose to ± spiculose; endostome with a low or rarely a high (as in Calyptrochaeta) basal membrane, the segments keeled and perforate or not; cilia poorly developed or absent. Calyptra mitrate, naked or pilose, fimbriate at base. Spores small, spherical.

The Daltoniaceae belong in the Hookeriales, an order that has attracted a great deal of systematic attention since c. 1970. W.R. Buck has published extensively on this group and has been responsible for many improvements in our understanding of the relationships in this large, diverse, and predominantly tropical group. According to Buck (1988) the characters that "hold together most of the genera are short leaf cells, complete lack of alar differentiation, exserted capsules, often roughened on setae, collenchymatous exothecial cells, rostrate opercula, baffle-like cross-walls in endostomal segments, and mitrate calyptrae". Despite the large number of relatively recent publications on the relationships of the Daltoniaceae and their allies (i.e. the Hookeriales), little consensus has emerged concerning boundaries between the component families.

Traditionally (Brotherus 1925) the Daltoniaceae were included in, or close to, the broadly defined Hookeriaceae. This broad and conservative concept of the Hookeriaceae was utilised by Streimann (1997; 1999; 2000) in his useful treatment for Australia.

However, the concept of the Daltoniaceae (and, by implication, the Hookeriaceae) presented here follows Goffinet et al. (2009). Seven N.Z. genera are included in the family here (Achrophyllum, Beeveria, Calyptrochaeta, Crosbya, Daltonia, Distichophyllum, and Ephemeropsis) from a total of 14 genera worldwide.

Goffinet et al. (2009) recognised seven families in the Hookeriales worldwide. Of these seven, three (Daltoniaceae, Hypopterygiaceae, and Saulomataceae) occur in N.Z. The much reduced Hookeriaceae sensu Goffinet et al. does not occur here.

Buck (1988, p. 33) has argued that Calyptrochaeta is anomalous in the Daltoniaceae because of its "weak costa, well-developed stem anatomy and curved seta", but it is retained here.